The theoretical aspect of this research aims at finding methods of abstract mathematical analysis which can be applied to pharmacokinetics and which may circumvent some of the problems of biological complexity and variability, and facilitate the use of empirical data to make practical predictions and plan therapeutic regimens. A more practical aspect has been the development of an interactive computer program DOSER designed to utilize clinical and literature data to assist in planning dosage schedules. Theoretical studies are presently pursuing the analysis of linear pharmacokinetic systems in terms of the so-called "impulse response," with regard to (a) the peak plasma or tissue levels obtained with different injection functions, (b) the rapid establishment and maintenance of desired plasma or tissue levels, and (c) the optimization of the injection function.